Micelle Aggregation Research Articles

A physicochemical investigation of the complex formation by β-cyclodextrin with Triton X-100 and Triton X-114 and their aggregation behaviour in aqueous solution: an experimental approach.

The complexation behavior and binding affinity of Triton X-100 (TX-100) and Triton X-114 (TX-114) with β-cyclodextrin (β-CD) were extensively studied in an aqueous medium using a comprehensive suite of experimental techniques. These techniques allowed for the evaluation of key physicochemical parameters, including critical micelle concentration (cmc), aggregation number (Nagg), Stern-Volmer constant, and particle size distribution. These metrics were instrumental in understanding the underlying mechanism of the host-guest interaction between β-CD and Triton-X. Dynamic light scattering (DLS) data provided strong evidence for the formation of inclusion complexes, demonstrating significant hydrophobic interactions between the hydrophobic regions of Triton-X and the cavity of β-CD. The disruption of micellar structures, caused by β-CD encapsulating the hydrophobic moieties of the surfactants, was clearly observed. This process also resulted in an increased CMC, further underscoring the impact of β-CD on the aggregation behavior of the surfactants. To quantify the interaction, the Benesi-Hildebrand method was utilized to determine the stoichiometry and binding constants of the β-CD/Triton-X complexes. The results confirmed a well-defined 1 : 1 binding mode, indicating the precise incorporation of the surfactant's hydrophobic tails into the β-CD cavity while leaving the hydrophilic regions exposed to the aqueous environment. This selective binding mechanism alters the thermodynamics of micellization and disrupts the native micellar equilibrium of the surfactant systems. This systematic and comparative investigation is among the few studies that thoroughly examine the interactions between Triton-X surfactants and β-CD. Such research not only enhances our understanding of these complexes, but also reveals their significant potential for various applications. In drug delivery, for example, β-CD/Triton-X complexes can improve the solubility, stability, and bioavailability of hydrophobic drugs. In supramolecular chemistry, these complexes serve as model systems for studying host-guest interactions and self-assembly processes. Furthermore, their ability to modulate surfactant behaviour opens avenues for their use in material science, cosmetics, and industrial formulations, where precise control over micelle formation and aggregation is essential. This study underscores the versatility and utility of β-CD in interacting with non-ionic surfactants, offering insights that can be applied to other amphiphilic systems and paving the way for innovative applications in diverse fields.

Study on the synthesis and properties of Gemini surfactant with ester spacers

Abstract A group of cationic Gemini surfactants with ester spacers, C12-E2-C12, C16-E2-C16, C18-E2-C18, were synthesized and confirmed by IR, 1H NMR and MS. The surface parameters of the synthesized Gemini surfactants including: the critical micelle concentration (CMC), the surface tension value at CMC (γ CMC), efficiency (pC 20), maximum surface excess (Γ max) and minimum surface area (A min), were obtained from surface tension measurements. These Gemini surfactants showed higher surface activity than the traditional monomeric surfactants. The thermodynamic parameters of the micellization process from conductivity measurements showed that the micellization was a spontaneous and exothermic process, and the micellization process became less favorable with decreasing alkyl chain length and increasing temperature. The micro polarity was evaluated from steady-state fluorescence spectra. It was found that the micelle aggregation number of Cn-E2-Cn aqueous solution gradually increased with the increase of alkyl chain.

Blending pectin and κ-carrageenan converted the liquid yogurt induced by pectin into the solid yogurt

Effects of 0.11 %–0.17 % pectin and the mixture of 0.03 % κ-carrageenan and 0.11 %–0.17 % pectin on texture and microstructure of yogurt were investigated in this work. Rheology analysis demonstrated that adding 0.11 %–0.17 % pectin before fermentation inhibited gelation of yogurt and liquid yogurt was formed. However, when the above κ-carrageenan/pectin mixture was added, yogurt was gelled and solid-like. It was demonstrated by CLSM that milk protein aggregated into separated particles in the liquid yogurt induced by pectin, while milk protein aggregated into a continuous network in the solid yogurt induced by the mixture. Adding 0.11 %–0.17 % pectin into the casein micelle suspension induced aggregation of casein micelles into separated particles, which was the same in the corresponding liquid yogurt samples. Moreover, casein micelles precipitated in the pectin/casein micelle mixtures after storage for 3 h. However, when the above mixture was added into the casein micelle suspension, tightly-connected casein micelle aggregates appeared and the resultant κ-carrageenan/pectin/casein micelle mixtures were stable after storage for 3 h. These results indicated that the pectin-casein micelle interaction played an essential role in formation of the liquid yogurt and κ-carrageenan altered this interaction. Thus, blending κ-carrageenan and pectin converted the liquid yogurt induced by pectin into the solid yogurt.

Green Synthesis of Polyesters Using Surfactant Catalysts in Microemulsions: The Role of Micelle Shape and Aggregation on Polymer Formation

Green Synthesis of Polyesters Using Surfactant Catalysts in Microemulsions: The Role of Micelle Shape and Aggregation on Polymer Formation

Surface engineered novel cationic surfactants with enhanced surface adsorption for environmental applications

Gemini Cationic Surfactants (GCS) have garnered significant attention due to their distinctive molecular structure, featuring two hydrophilic head groups associated with a hydrophobic spacer. This distinctive configuration enables diverse applications across various fields. Hence, the current study introduces a novel series of GCSs, ethanediyl-1,2-bis[di(2-hydroxypropyl) alkylammonium] dibromide (Cn-C2-Cn[IsoPr(OH)2; n = 9, 12 and 14) and comprehensively explore their properties, highlighting their promising antimicrobial activity. The synthesis of GCSs was validated using 1H NMR and IR spectroscopy. Dynamic Light Scattering was employed to determine the dimensions of Gemini surfactant aggregates in aqueous solutions. Surface tension analysis determined critical concentrations of micelle (CMC), minimum surface area (Amin) and concentration of surface excess (Γmax). Physicochemical properties were assessed through conductivity and surface tension analyses in aqueous solutions. The CMC, Amin and Γmax values decrease as alkyl chain length extends. Surface tension data revealed strong adsorption of GCSs at interfaces. π values (mN/m) ranged from 36.7 (C14C2C14[Iso-Pr(OH)]2) to 45.3 (C9C2C9[Iso-Pr(OH)]2). Conductivity and surface tension measurements further characterized Gemini surfactants in aqueous environments at 298 K. The size of the micelle aggregates varied between C9C2C9[Iso-Pr(OH)]2 (1.2885 nm) and C14C2C14[Iso-Pr(OH)]2 (1.9210 nm), highlighting the impact of chain length on micelle size. Hence, the study highlights significant effect of the chain lengths on Gemini cationic surfactants’ self-assembly in dilute aqueous environments. Antimicrobial tests demonstrated significant activity of Cn-C2-Cn[IsoPr(OH)]2 GCSs at varying concentrations. Antimicrobial tests showed the significant antimicrobial potential of these GCS compounds, suggesting their potential and promising applications in medical, hygiene, environmental sanitation and advanced materials sectors.

Effect of Hydrophilic Function Groups on the Properties of Short‐Chain Fluorocarbon Surfactants

AbstractShort‐chain fluorocarbon surfactants grafted with alcohol, carboxyl and ester functional groups were prepared by quaternization with short‐chain perfluorobutyl sulfonyl fluoride as raw material. The structures of surfactants were characterized by infrared spectroscopy, nuclear magnetic resonance and mass spectrum. The surface activity, micelle formation process and micelle aggregation behavior of surfactants were studied by surface tensiometer, dynamic light scattering particle size analyzer and fluorescent spectrophotometer. The results show that the critical micelle concentration (CMC) of surfactants are 19.3, 7.8 and 2.2 mmol L−1, and the surface tension of the surfactant solution at CMC are as low as 17.3, 19.2 and 18.5 mN m−1, respectively. The standard Gibbs free energy ( ) values of surfactants are negative, and the absolute values of are less than the standard Gibbs adsorption energy ( ), illustrating that the adsorption process is easier than the micelle formation process. In addition, the size distribution of the aggregates is much larger than that of spherical micelles, showing that the surfactant self‐assembled into larger aggregates in solution. The grafted hydrophilic functional groups show a significant effect on the performance of surfactants. The ester‐based surfactant has a lower CMC value, which has the advantages of small dosage, good economy and excellent application value.

Self-Assembly Hypoxic and ROS Dual Response Nano Prodrug as a New Therapeutic Approach for Glaucoma Treatments.

Glaucoma is an irreversible blinding eye disease characterized by retinal ganglion cell (RGC) death.Previous studies have demonstrated that protecting mitochondria and activating the CaMKII/CREB signaling pathway can effectively protect RGC and axon. However, currently treatments are often unsatisfactory, and the pathogenesis of glaucoma requires further elucidation. In this study, a ROS-responsive dual drug conjugate (OLN monomer) is first designed that simultaneously bonds nicotinamide and oleic acid. The conjugate self-assembled into nanoparticles (uhOLN-NPs) through the aggregation of multiple micelles and possesses ROS scavenging capability. Then, a polymer with a hypoxic response function is designed, which encapsulates uhOLN-NPs to form nanoparticles with hypoxic and ROS responses (HOLN-NPs). Under hypoxia in RGCs, the azo bond of HOLN-NPs breaks and releases uhOLN-NPs. Meanwhile, under high ROS conditions, the thioketone bond broke, leading to the dissociation of nano-prodrug. The released nicotinamide and oleic acid co-scavenge ROS and activate the CaMKII/CREB pathway, protecting mitochondria in RGCs. HOLN-NPs exhibit a significantly superior protective effect on R28 cells in glutamate models of glaucoma. The accumulation of HOLN-NPs in retinal RGCs lead to significant inhibition of RGC apoptosis and axonal damage in vivo. Notably, HOLN-NPs provide a new therapeutic approach for patients with neurodegenerative disease.

Exploration of dynamic interaction between β-lactoglobulin and casein micelles during UHT milk process

The protein aggregation induced by UHT treatment shortens the shelf life of UHT milk. However, the mechanism of β-Lg induced casein micelle aggregation remains unclear. Herein, the dynamic interaction between β-Lg and casein micelles during UHT processing was investigated by experimental techniques and molecular dynamics simulations. Results showed that β-Lg decreased the stability of casein micelles, increased their size and zeta potential. Raman and FTIR spectra analysis suggested that hydrogen and disulfide bonds facilitated their interaction. Cryo-TEM showed that the formation of the casein micelle/β-Lg complex involved rigid binding, flexible linking, and severe cross-linking aggregation during UHT processing. SAXS and MST demonstrated β-Lg bound to κ-casein on micelle surfaces with a dissociation constant (Kd) of 3.84 ± 1.14 μm. Molecular docking and dynamic simulations identified the interacting amino acid residues and clarified that electrostatic and van der Waals forces drove the interaction. UHT treatment increased hydrogen bonds and decreased total binding energy. The non-covalent binding promoted the formation of disulfide bonds between β-Lg and casein micelles under heat treatment. Ultimately, it was concluded that non-covalent interaction and disulfide bonding resulted in casein micelle/β-Lg aggregates. These findings provided scientific insights into protein aggregation in UHT milk.

Influence of critical micelle concentration of choline-based long chain fatty acid soaps on their antibacterial activity against Methicillin resistant Staphylococcus aureus

HypothesisAntimicrobial resistance (AMR) is a pressing global health concern. ESKAPEE pathogens, such as Methicillin-resistant Staphylococcus aureus (MRSA) are notable of concern in healthcare settings due to their resistance to critical antibiotics. To combat AMR, the development of alternatives such as bacterial membrane-active agents is crucial. Fatty acids (FAs) have emerged as a sustainable, antibiotic-free solution with inherent antibacterial activity. However, long chain saturated fatty acids (LCFAs) sodium soaps exhibit poorly antibacterial properties in comparison to short chain FAs, believed to be linked to limited solubility in aqueous media. ExperimentsWe employed choline as a chaotropic organic counter-ion to enhance the solubility of LCFAs and investigated their antibacterial effects against MRSA. The optimal medium conditions for micelle formation for LCFAs was first investigated. Then, we determined the critical micelle concentration (CMC), micellar morphology, and aggregation number through surface tension measurements and small angle neutron scattering experiments. Antimicrobial activity was assessed using minimum bactericidal concentration (MBC) assays and time-kill experiments. FindingsWe have identified conditions where LCFAs are effective against MRSA for the first time, providing valuable insights for developing new antibacterial agents to fight AMR. LCFAs need to be used above their Krafft temperatures and CMC to exhibit antibacterial efficacy.

An application of hierarchical MgAl hydrotalcite in the highly efficient treatment of oilfield macromolecular contaminants.

In this work, salicylic acid (SA) was used to induce the self-assembly of octadecyl trimethyl ammonium chloride (OTAC), a cationic surfactant, into three-dimensional wormlike micelle aggregates. These aggregates act as a soft template for hierarchical MgAl hydrotalcite (LDH) to create a multi-level pore structure adsorption material. Scanning electron microscopy characterization showed that the surface of the hierarchical hydrotalcite exhibited a dense layered structure, unlike the monolayer structure of ordinary hydrotalcite. Furthermore, the hierarchical MgAl-LDH possesses a significantly larger specific surface area (113.94 m2/g) and wide pore size distribution ranging more extensively from 2 to 80nm, which significantly has an impressive adsorption effect on sulfonated lignite (SL), with a maximum adsorption capacity of 192.7mg/g at pH = 7. Extensive research has been conducted on the adsorption mechanism of hierarchical MgAl-LDH, attributing it to surface adsorption due to the unique multi-level structure of the adsorbent. After two cycles of regeneration experiments, the adsorption capacity of the adsorbent remained at a high level of 179.1mg/g, demonstrating the excellent renewability of hierarchical MgAl-LDH. Moreover, the hierarchical hydrotalcite showed high adsorption capacity in the adsorption of sulfonated lignite, which was attributed to its larger specific surface area and superior pore structure to expose more active sites.

Rationale Design for Anchoring Pendant Groups of Zwitterionic Polymeric Medical Coatings.

A biocompatible and antifouling polymeric medical coating was developed through rational design for anchoring pendant groups for the modification of stainless steel. Zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) was copolymerized individually with three anchoring monomers of carboxyl acrylamides with different alkyl spacers, including acryloylglycine (2-AE), 6-acrylamidohexanoic acid (6-AH), and 11-acrylamidoundecanoic acid (11-AU). The carboxylic acid groups are responsible for the stable grafting of copolymers onto stainless steel via a coordinative interaction with metal oxides. Due to hydrophobic interaction and hydrogen bonding, the anchoring monomers enable the formation of self-assembling structures in solution and at a metallic interface, which can play an important role in the thin film formation and functionality of the coatings. Therefore, surface characterizations of anchoring monomers on stainless steel were conducted to analyze the packing density and strength of the intermolecular hydrogen bonds. The corresponding copolymers were synthesized, and their aggregate structures were assessed, showing micelle aggregation for copolymers with higher hydrophobic compositions. The synergistic effects of inter/intramolecular interactions and hydrophobicity of the anchoring monomers result in the diversity of the thickness, surface coverage, wettability, and friction of the polymeric coatings on stainless steel. More importantly, the antifouling properties of the coatings against bacteria and proteins were strongly correlated to thin film formation. Ultimately, the key lies in deciphering the molecular structure of the anchoring pendants in thin film formation and assessing the effectiveness of the coatings, which led to the development of medical coatings through the graft-onto approach.

Efficient Catalyst-Free One-Pot Synthesis of Polysaccharide-Polypeptide Hydrogels in Aqueous Solution.

The preparation of polysaccharide-peptide hydrogels usually involves multiple synthetic steps, thus reducing the effectiveness and practicality of these approaches. Inspired by recent discoveries in aqueous N-carboxyanhydride (NCA) ring-opening polymerization (ROP) and ring-opening polymerization-induced nanogelation, we present an aqueous one-pot strategy to prepare polysaccharide-polypeptide hydrogels. In this study, water-soluble polysaccharide carboxymethyl chitosan is used as the macromolecular initiator to prepare polysaccharide-polypeptide copolymers through the aqueous ROP of NCA. The catalyst-free approach afforded hydrogels with properties that could be controlled by adjusting the type and amount of NCA used, with the elastic modulus ranging from 50 Pa to 18000 Pa. The hydrogen bond-cross-linked hydrogel exhibited self-healing and injectable properties. Morphology characterization revealed that micelles were formed in the early stage of reaction, suggesting that the polymerization follows an aqueous ring-opening polymerization-induced self-assembly (ROPISA) mechanism and that aggregation of micelles during the reaction caused the gelation. Moreover, the hydrogels displayed high swelling ratios (>95% water content), and hemolysis and cytotoxicity experiments demonstrated that the hydrogels had excellent biocompatibility, indicating their potential in medical applications.

Coarse grained MD simulation of bulk and interfacial behavior of mixture of CTAB/SDS surfactants.

This study involves simulating the process of inhibiting corrosion through the formation of micelles by surfactants and their deposition on iron (Fe) surfaces. The primary focus is on examining CTAB/SDS mixtures in aqueous solutions with different concentrations. Micelle properties, including size, shape, aggregation number, cluster size, and surfactant diffusion, were calculated and validated with experimental data. The coarse-grained Fe surface was modeled and validated against experimental water contact-angle data. Subsequently, the deposition of CTAB/SDS mixtures on the Fe surface and air-water interface was studied systematically. We found that the relative ratio of CTAB/SDS in the solution directly influences surfactant deposition behavior, which might impact the corrosion inhibition efficiency. All the MD simulations were performed using the GROMACS software with MARTINI2 force field and Martini polar water. The molecules are packed using PACKMOL software. Both NVT and NPT simulations are caried out at temperature and pressure of 303 K and 1 bar respectively, with a nonbonded interaction cut-off (rcut) of 1.1 nm. The LJ potential was shifted from 0.9 nm to rcut, while the electrostatic potential was shifted from 0.0 nm to rcut. For electrostatics, reaction-field coulomb type is used, relative dielectric constant (epsilon-r) and the reaction field dielectric constant (epsilon-rf) are equal to 2.5 and infinity respectively. The dielectric constant below rcut is epsilon-r, and beyond the cut-off is epsilon-rf. Coulomb-modifier used as potential-shift which leads to shift in the coulomb potential by a constant such that it is zero at the rcut. This makes the potential of the integral of the force . The neighbor list was updated every 10 steps, employing a neighbor list cut-off equal to rcut. Using a polar water model, we used a constant time step of 0.02 ps throughout the simulation. The used epsilon-r = 2.5, is recommended for polar water.

Characterization of Surfactant Spheroidal Micelle Structure for Pharmaceutical Applications: A Novel Analytical Framework.

We introduce an innovative theoretical framework tailored for the analysis of Pair Distribution Function (PDF) data derived from Small-Angle X-ray Scattering (SAXS) measurements of core-shell micelles. The new approach involves the exploitation of the first derivative of the PDF and the derivation of analytical equations to solve the core-shell micelle structure under the hypothesis of a spheroidal shape. These analytical equations enable us to determine the micelle's aggregation number, degree of ellipticity, and contrast in electron density between the core-shell and shell-buffer regions after having determined the whole micelle size and its shell size from the analysis of the first derivative of the PDF. We have formulated an overdetermined system of analytical equations based on the unknowns that characterize the micelle structure. This allows us to establish a Figure of Merit, which is utilized to identify the most reliable solution within the system of equations.

Preparation of liquid yogurt in the presence of pectin and its formation mechanism

We had previously observed that adding pectin into milk before fermentation inhibited gelation of yogurt but did not affect the pH. Thus, this work aimed to prepare such liquid yogurt and clarify its formation mechanism. It was found that liquid yogurt was obtained in the presence of 0.10%–0.20% pectin. However, at lower or higher pectin concentrations, yogurt was gelled. Confocal laser scanning microscopy analysis demonstrated that 0.10%–0.20% pectin induced milk protein aggregating into separated particles rather than a continuous network, which explained why liquid yogurt was formed. Moreover, adding 0.10%–0.20% pectin into the casein micelle suspension induced aggregation of casein micelles at pH 6.8. After pH decreased to 4.3, casein micelles showed more aggregation but they were still separated particles, which was the same in the corresponding yogurt samples. These results suggested that pectin changed the aggregation mode of casein micelles and induced formation of liquid yogurt.

Effect of Tannic Acid Concentrations on Temperature-Sensitive Sol-Gel Transition and Stability of Tannic Acid/Pluronic F127 Composite Hydrogels.

Recently, interest in polyphenol-containing composite adhesives for various biomedical applications has been growing. Tannic acid (TA) is a polyphenolic compound with advantageous properties, including antioxidant and antimicrobial properties. Additionally, TA contains multiple hydroxyl groups that exhibit biological activity by forming hydrogen bonds with proteins and biomacromolecules. Furthermore, TA-containing polymer composites exhibit excellent tissue adhesion properties. In this study, the gelation behavior and adhesion forces of TA/Pluronic F127 (TA/PluF) composite hydrogels were investigated by varying the TA and PluF concentrations. PluF (above 16 wt%) alone showed temperature-responsive gelation behavior because of the closely packed micelle aggregates. After the addition of a small amount of TA, the TA/PluF hydrogels showed thermosensitive behavior similar to that of PluF hydrogels. However, the TA/PluF hydrogels containing more than 10 wt% TA completely suppressed the thermo-responsive gelation kinetics of PluF, which may have been due to the hydrogen bonds between TA and PluF. In addition, TA/PluF hydrogels with 40 wt% TA showed excellent tissue adhesion properties and bursting pressure in porcine intestinal tissues. These results are expected to aid in understanding the use of mixtures of TA and thermosensitive block copolymers to fabricate adhesive hydrogels for versatile biomedical applications.

Effect of polysaccharide-protein interactions on the multi-scale structure of hybrid micellar casein-xanthan gum systems

This study reports on the effect of pH and polysaccharide concentration (protein:polysaccharide ratios of 95:5, 85:15 and 75:25) on the interactions established between xanthan gum (XG) and micellar casein (MC), investigating the impact on the type of structures formed at the micro- and nanoscale. At pH ≥ 6, the micellar casein formed stable suspensions where micelles with diameters of ca. 130–150 nm showed a compact inner structure stabilised by colloidal calcium phosphate (CCP) nanoclusters, while at pH ≤ 3, a more loosely packed interconnected network structure, stabilised by protein-protein interactions, was noted. The addition of XG, even at low MC:XG ratios (95:5), resulted in increased stability of the system, preventing the formation of micelle aggregates at the microscale, and reducing the pH range at which casein precipitated close to the isoelectric point. For all the XG loadings, coacervates were formed at pH = 2–3 due to polysaccharide-protein electrostatic interactions, leading to separation into a solid gel-like phase composed of polysaccharide-protein fibrillar structures and a liquid phase rich in protein. At the nanoscale, XG was mostly coating the micelles and filling in the inner water channels when added at MC:XG ratios ≤85:15, while the higher polysaccharide content at the ratio 75:25 allowed to form an interconnected structure. Therefore, by adjusting pH and XG concentration, it is possible to improve casein stability, reduce agglomeration and manipulate the size of protein-polysaccharide complexes formed. This will be of great relevance for the development of novel food formulations with improved stability and modulated sensory and nutritional properties.

The effect of agar on rheological properties and thermal stability of rennet-induced casein micelle gel

Effects of agar on the rheological property and heat stability of casein micelle gels induced by rennet were investigated. The interactions between casein micelle and agar were investigated. Electrostatic interactions between casein micelle and agar were not observed. The movement of agar characteristic bonds indicated the hydrogen bond interaction existed in the casein micelle/agar mixture. The addition of agar promoted the casein micelles aggregation and decreased the rennet coagulation time (RCT) and the storage modulus (G'). The strip-like network microstructure changed into a sheet-like network after the addition of agar. The composite gels were present as a bicontinuous phase structure. The agar and protein were both present as continuous phases. The addition of 0.5% agar increased the water holding capacity (WHC) from 63.30% to 92.44% and decreased the gel hardness from 73.41 g to 60.57 g. The protein digestion rate of gels increased after agar addition during gastric digestion. The WHC increased from 35.20% to 83.56% and the microstructure of gels improved by the addition of 0.5% agar after heating at 80 °C for 30 min. In conclusion, the WHC and thermal stability of the gels improved after the addition of agar.

Repeated Aqueous Film-Forming Foams Applications: Impacts on Polyfluoroalkyl Substances Retention in Saturated Soil.

Historical practices at firefighter-training areas involved repeated aqueous film-forming foams (AFFFs) applications, resulting in source zones characterized by high concentrations of perfluoroalkyl and polyfluoroalkyl substances (PFAS). Repeated applications of AFFF composed of 14 anionic and 23 zwitterionic perfluoroalkyl substances (PFAS) were conducted on a single one-dimensional saturated soil column to quantify PFAS retention. An electrofluorination-based (3M) Milspec AFFF, which was above the mixture's critical micelle concentration (CMC), was at application strength (3%, v/v). Retention and retardation of PFAS mass increased with each successive AFFF addition, although the PFAS concentration profiles for subsequent applications differed from the initial. Greater degree of mass retention and retardation correlated with longer PFAS carbon-fluorine chain length and charged-headgroup type and as a function of AFFF application number. Anionic PFAS were increasingly retained with each subsequent AFFF application, while zwitterionic PFAS exhibited an alternating pattern of sorption and desorption. Surfactant-surfactant adsorption and competition during repeat AFFF applications that are at concentrations above the CMC resulted in adsorbed PFAS from the first application, changing the nature of the soil surface with preferential sorption of anionic PFAS and release of zwitterionic PFAS due to competitive elution. Applying a polyparameter quantitative structure-property relationship developed to describe sorption of AFFF-derived PFAS to uncontaminated, saturated soil was attempted for our experimental conditions. The model had been derived for data where AFFF is below the apparent CMC and our experimental conditions that included the presence of mixed micelles (aggregates consisting of different kinds of surfactants that exhibit characteristics properties different from micelles composed of a single surfactant) resulted in overall PFAS mass retained by an average of 27.3% ± 2.7% (standard error) above the predicted values. The correlation was significantly improved by adding a "micelle parameter" to account for cases where the applied AFFF was above the apparent CMC. Our results highlight the importance of interactions between the AFFF components that can only be investigated by employing complex PFAS mixtures at concentrations present in actual AFFF at application strength, which are above their apparent CMC. In firefighter-training areas (AFFF source zones), competitive desorption of PFAS may result in downgradient PFAS retention when desorbed PFAS become resorbed to uncontaminated soil.

The aggregation of casein micelles induced by Ca2+ during in vitro digestion: effects on the release of loaded anthocyanins.

Colloidal calcium phosphate (CCP) confers a modifiable structure to micellar casein (MC), which endows it with potential advantages as a delivery carrier. However, it is difficult to achieve multipattern release of the core material in the intestine with MC as a single wall. In this study, we prepared an anthocyanin-casein-based delivery system utilizing MC with different freezing degrees as the wall material with the objective of achieving the controlled release of anthocyanin as the model core in the intestine. The results showed that freezing could significantly reduce the CCP level up to 50%. Static in vitro simulated digestion with the addition of exogenous Ca2+ showed that the designed delivery system exhibited low anthocyanin release (15%-35%) in the gastric tract. The pattern of release in the intestine depended on the CCP dissociation degree. High and low dissociation degrees corresponded to slow release (from 15% to 65% within 2 h) and burst release (from 35% to 90% within 5 min), respectively. WAXS/SAXS analysis revealed that exogenous serum Ca2+ inherent in simulated gastric fluid and endogenous serum Ca2+ induced by CCP dissociation was synergistically involved in the reconstitution of CCP-mediated nanoclusters and large aggregates. The freezing degree of MC determined the endogenous serum Ca2+ level, which influenced the gastric aggregation behavior of wall MC and ultimately led to a fairly different gastrointestinal release behavior of anthocyanins.